You're not the first to tell me it'* not supposed to be that high. Having said that, the manual says that the bcm controls the charging circuit'* duty cycle and output. One state is the sulfate mode, which ramps the duty cycle higher and voltage hours up to 15 volts or higher for the duration of that cycle. It'* worded a little differently in the manual but I don't have it in front of me. Either way, the computer obviously has more control over what hours on under the hood, including battery charging than my other older vehicles in the last ever did. My mechanic told me to disregard the displayed voltage because it may not be accurate. I have had a meter on the battery before when the engine was running, but it was a while ago. I don't recall if the readings were dramatically different or not. I'm almost convinced I have an alternator problem.

possibly if the something is wrong where it charges for a while and its not working and then it might go to that mode. i dont think the voltage would go up if the alt was bad. seems like i said a corrosion or connection issue.

I'll check those connections for corrosion and get back to you.

ok so that past few days has seen temperatures dip to minus 16 degrees celsius. Since plugging in the block heater doesn't work until the temperature drops to -18C or colder, then the trickle charger has seemed to do the trick. Sucks, but it'* keeping me from taking the bus!!!!

Well that is good news that the trickle charger is keeping the battery up to cranking speed!
Have the battery tested by someone with an electronic load & charging system tester.
Did you have a look at the terminals are they clean & tight?

The terminals are in decent shape. The clamps are the factory originals, and I've never like the design. The don't seem to have enough clamping force. You can turn them a bit even when full tight. I bought two new post clamps and will install those this weekend. Also,I haven't had any further starting issues since I've been putting the trickle charger on nightly.

My Pk Ave originally had Gm side post connectors. The corrosion and connection was poor.
Used Marine terminals and added extra thicker ground wire. Top post connections still need to be checked when it gets cold out. They do loosen off, movement not good.
I use a mega powerful Odyssey AGM battery. No venting and don't have to worry about corrosion.

If you do have a lead acid battery/top post for 3 $ install some battery terminal washers. These felt washers reduce corrosion big time.